This invention relates to 5-fluoro-2'-deoxyuridine derivatives and a process for the preparation thereof.
An antitumor substance 5-fluorouracil (5-FU) has the efficacy against a wide range of malignant tumor including brest cancer, gastric cancer, lung cancer, pancreatic cancer, hepatoma, uterine cancer, etc. when used singly or in combination with other drugs. However, with regard to the efficacy, side effects, pharmacokinetics, etc. of 5-FU, further improvement is wanted and intensive studies are actively conducted by many specialists in the medical circles. 5-FU is transformed intracellularly into 5-fluoro-2'-deoxyuridine-5'-phosphate, which inhibits thymidylate synthetase and this is generally known to be the major mechanism of its anticancer effect. 5-Fluoro-2'-deoxyuridine (5-FUdR) has a much stronger cytotoxic activity in vitro as compared with 5-FU, because it is more akin to active form than 5-FU. However, the activity of 5-FUdR in vivo is weak in spite of its strong activity in vitro. The improper pharmacokinetics of 5-FUdR may be the cause of the discrepancy between its activity in vitro and in vivo.
Various 5-FUdR derivatives have been prepared seeking for improved activities. For instance, 3-acyl-5-FUdR (Japanese Patent Laying-open No. 163586/79), 3',5'-diacyl-5-FUdR (Epitome of 100th anniversary lecture meeting of the Pharmacological Society of Japan, p.321, 1980), 5-FUdR whose 3-position and 3',5'-position are all acylated (Japanese Patent Laying-Open Nos. 113795/'81, 113796/'81, and 113797/'81) are known.
Also derivatives of 5-fluorouridine (5-FUR) having a phosphodiester bond at the 5'-position are known (Japanese Patent Laying-Open No. 29938/'78). However, even these derivatives are not satisfactory enough in view of their anticancer effects and side effects.